In an alkaline battery, negatively charged anions migrate from a cathode across an alkaline electrolyte solution to an anode, while positively charged cations migrate from the anode across the alkaline electrolyte solution to the cathode. A separator is interposed between the cathode and the anode to separate these electrodes and prevent short-circuiting.
Such an alkaline battery separator needs to meet various requirements. For instance, such a separator should: (1) prevent internal short-circuiting between the cathode and the anode; (2) have satisfactory electrolyte absorption capacity to cause sufficient electrogenic reactions, while having good ion conduction as well as low electric resistance; (3) occupies a small space when incorporated into a battery so as to increase the amount of cathode and anode active materials (and therefore increasing the battery life); and (4) withstand, after incorporated into a battery, buckling caused by impacts due to vibrations or accidental drops during transport or handling, which may lead to internal short-circuiting of the battery.
For example, Patent Document 1 listed below (JP Laid-open Patent Publication No. 10-092411) discloses a separator paper for electrically isolating an anode active material and a cathode active material of an alkaline-battery, wherein said separator paper comprises a dense layer for keeping its denseness to prevent electrical internal shortage of said two active materials, and a liquid impregnating layer for increasing the liquid impregnate ratio of the electrolyte within the battery, with said dense layer and said liquid impregnate layer being integrally laminated.
Such a separator paper requires cellulose fiber(s) for the liquid impregnate layer having a freeness (CSF: Canadian standard freeness) value of no less than 700 ml, in order to prevent significant loss of liquid impregnate ratio of the separator paper.